Early embryo mortality occurs mainly until 16 days post-conception in cattle (Diskin et al., 2016;Hill et al., 2000), and such a problem seems to be of higher occurrence for in vitro-produced (IVP) bovine embryos Bertolini, Mason et al., 2002).A higher rate of embryonic mortality seen for IVP embryos has been associated with initial growth retardation and with changes in gene

The influence of two oxygen tensions (5 and 20%) on fertilization, cleavage, development, and morphological quality of canine embryos produced in vitro was investigated. To assess embryo production, canine oocytes (N = 608) were matured in vitro at 20% oxygen tension in TCM 199 supplemented with glucose (11 mM) and 0.1% polyvinyl alcohol. Oocytes and sperm were coincubated at 37 °C for 24 hours in serum-free medium. Subsequently, presumptive zygotes were cultured in vitro in synthetic oviductal fluid in either 5% CO2 in air (20% oxygen; N = 298) or 5% O2, 5% CO2 and 90% N2 (5% oxygen; N = 310) for 7 days. Regardless of the oxygen concentration (5 vs. 20%), rates of pronucleus formation, cleavage, and embryo development up to the eight-cell stage did not differ (46/310 [14.8%] vs. 35/298 [11.7%], respectively; P > 0.05). Moreover, similar proportions of embryos developed in 20 and 5% oxygen tensions (18/298 vs. 27/310). The oocyte nuclear maturation (metaphase II), in terms of decondensed sperm heads, pronucleus formation, cleavage, and embryo development, was similar (P = 0.299) between the atmospheric (20% O2; 12.4% [37/298]) and reduced oxygen tensions (5% O2; 15.8% [49/310]) at all steps of the in vitro culture (IVC) after in vitro fertilization (IVF). To our knowledge, this was the first study that demonstrated that canine embryos can be produced using a low-oxygen in vitro culture system. Both oxygen tensions (5 and 20%) resulted in similar embryonic development and therefore were feasible for IVC of canine oocytes.

No abstract

No abstract

Important genomic imprinting changes usually occur following the in vitro production (IVP) of bovine embryos, especially in the imprinting pattern of components of the IGF system. This study aimed to evaluate the effects of a transient episomal overexpression of the IGF2 gene in bovine IVP embryos following embryo cytoplasmic microinjection (CMI) at the 1‐cell stage on embryo survival, early and late developmental kinetics and morphological quality up to Day 7 of development. Selected cumulus–oocyte complexes (COCs) were matured and fertilized in vitro and subsequently segregated into six experimental groups: non‐CMI control group and five CMI groups at increasing doses (0, 10, 20, 40 and 80 ng/μl) of a GFP vector built for the episomal expression of bovine IGF2. Zygote CMI was effective in delivering the expression vector into the ooplasm, irrespective of the groups, with 58% of positive GFP fluorescence in Day 7 blastocysts. Considering developmental rates and late embryo kinetics, the 10‐ng/μl CMI vector dose promoted a lower blastocyst rate (10.4%), but for blastocysts at more advanced stages of development (93.0% blastocysts and expanded blastocysts), and higher number of cells (116.0 ± 3.0) than non‐CMI controls (23.3%, 75.0% and 75.0 ± 6.8 were obtained, respectively). In conclusion, CMI at the 1‐cell stage did not compromise subsequent in vitro development of surviving embryos, with the 10‐ng/μl group demonstrating a possible growth‐promoting effect of the IGF2 gene on embryo development, from the 1‐cell to the blastocyst stage.